雷射彩色打標成品顏色品質控制之研究

Abstract

雷射彩色打標加工技術所涉及的機制相當複雜，目前仍缺乏完整的理論模型。而在實務上，雷射彩色打標加工過程中，大量使用試誤法來建立加工參數與打標成品之間的對應關係，然而實際上，在雷射打標加工的過程中會產生數種特殊外觀如彩虹紋、表面成色不均及隨觀察角變化顏色等，這些特殊外觀大多難以被量化，並且無論使用試誤法或機器學習建模，皆大大增加建模的難度。本研究透過研究各參數在雷射彩色打標加工時對顏色的效應，提出三種特殊外觀與參數關係的歸納結果，推測其形成機制，使特殊外觀由不可控變為可控，同時歸納脈衝步距、脈衝頻率、單發脈衝能量及脈衝寬度參數效應，釐清顏色生成規律，以利使用者在因環境因素、模型不完整等原因導致打標成品顏色與預期不符時，能正確地對參數做出微調。 為了解雷射彩色打標加工中，參數與打標成品顏色的對應關係，本研究進行全因子實驗，並搭配 CIELAB 標準進行色彩量測。 全因子實驗顯示在脈衝步距過短，或單發脈衝能量過長時，打標成品顏色會呈現黯淡的灰、褐色或棕黑色，而若單發脈衝能量過低，或者脈衝步距過高，則會使打標成品顏色維持原色，其餘的參數組合則可以製造出鮮豔的彩色。實驗結果亦顯示打標成品顏色不均勻的現象具有重複性，且可利用參數微調的方式控制，出現在彩色區域與灰、褐色、棕黑色及原色的交界處。 可藉由微調參數的方式來避免打標成品顏色不均勻，但為使微調參數的過程中所造成的色差最小化，研究了各加工參數對顏色之效應，結果顯示顏色同樣主要由單發脈衝能量與脈衝步距決定，並且功率增加與脈衝步距降低皆使反射光譜高峰之波長變長、成品表面粗糙度增加以及成品顏色彩度降低，同時調整兩參數可使調整參數所造成的色差最小化。脈衝寬度 12ns 以下在加工單道時出現凹痕，12ns 以上則出現週期性重熔痕跡，同時顏色不均勻的現象在脈衝寬度越高時越容易發生。

The mechanisms involved in laser color marking technology are highly complex, and a comprehensive theoretical model is still lacking. In practical applications, trial-and-error methods are extensively employed to establish the relationship between processing parameters and the resulting marked products. However, in the actual laser marking process, several unique visual effects may emerge, such as rainbow patterns, uneven surface coloration, and color variations depending on the observation angle. These unique appearances are generally difficult to quantify, making the modeling process significantly more challenging, whether using trial-and-error methods or machine learning approaches. This study investigates the effects of various parameters on color during laser color marking, proposing three types of correlations between unique visual effects and parameters, and hypothesizing the underlying mechanisms. The goal is to transition these unique appearances from being uncontrollable to controllable. Additionally, the effects of parameters such as pulse spacing, pulse frequency, single-pulse energy, and pulse width are summarized to clarify the principles of color formation. This will enable users to make precise adjustments to parameters when the color of the marked product deviates from expectations due to environmental factors or incomplete models.

To understand the relationship between parameters and the color of the marked product during laser color marking, a full factorial experiment was conducted, with color measurements performed using the CIELAB standard.

The full factorial experiment revealed that when the pulse spacing is too short or the single-pulse energy is too high, the resulting marked product exhibits dull gray, brown, or dark brown colors. Conversely, when the single-pulse energy is too low or the pulse spacing is too large, the marked product tends to maintain its original color. Other parameter combinations can produce vibrant colors. The experiment also showed that the phenomenon of uneven color distribution is reproducible and can be controlled through fine-tuning of parameters, particularly at the boundaries between colored areas and gray, brown, dark brown, or original colors.

By fine-tuning the parameters, it is possible to avoid uneven color distribution in the marked product. However, to minimize color deviations during the adjustment process, the effects of various processing parameters on color were studied. The results indicated that color is primarily determined by single-pulse energy and pulse spacing, and that increasing power and decreasing pulse spacing both lead to longer peak wavelengths in the reflection spectrum, increased surface roughness of the product, and reduced color saturation. Adjusting these two parameters together can minimize color deviations caused by parameter adjustments. Pulse widths below 12 ns resulted in indentations during single-pass processing, while pulse widths above 12 ns produced periodic remelting traces, with uneven coloration becoming more pronounced as the pulse width increases.